[free/open source - Windows, Macintosh, Unix] Download FITS viewers for various platforms.
http://www.cv.nrao.edu/~bcotton/fitsview.html
Displays HPGL/HPGL2 graphic files, with output to printers and plotters, and PDF, DXF, TIFF, JPEG, and BITMAP files. Also allows text search and measurement of distances.
http://homepage2.nifty.com/ploview/ehp.htm
Viewers and converters for HPGL, Gerber, and Excellon files, with an ActiveX Control version.
http://www.softwarecompanions.com/
TimingTool is a free to use timing diagram editor that is built around the Si2 TDML standard. VHDL or Verilog can be automatically generated from saved TDML.
http://www.timingtool.com/
Suite of products for viewing AutoCAD drawings online and offline, with redlining and hyperlink capabilities.
http://www.drdwg.com/
DOS CAD/CAM software designed to help you work with RS-274 (often called Gerber) photoplotter and NC drill CAD output data, also supports HPGL and Quest (Marconi Emma) plotter formats
http://www.graphicode.com/index.cfm?section=Download&page=5
An Open Source program that allows to open, view, print and convert DWG or DXF files up to version 2002 on the Linux platform.
http://lx-viewer.sourceforge.net/
On-line conferencing over the internet, with 3D CAD visualisation, measuring, annotation, and 3D CAD file sharing in IGES, VRML, VDA and 3D DXF files formats
http://www.materialise.com/mt.asp?mp=cm_main